Effects of Combined Application of Trichoderma afroharzianum and Bacillus velezensis on Quinoa Basal Stem Rot and Rhizosphere Microecology

doi:10.13560/j.cnki.biotech.bull.1985.2025-1271

Abstract

Abstract:

Objective This study evaluated the control efficacy of a wettable powder formulation containing Trichoderma afroharzianum LMNS-M9 combined with another formulation containing Bacillus velezensis YPTJ-1 against quinoa basal stem rot and its regulatory effects on the rhizosphere microbial community structure. Method We conducted pot experiments to compare the control efficacy of the single and combined microbial agents, and we evaluated the efficacy of the combined agent at different concentrations in field experiments. We then used high-throughput sequencing to analyze the effects of the different treatments on the quinoa rhizosphere microbial communities. Result The control efficacy of the combined microbial agent against quinoa basal stem rot in the pot experiment was 73.55%, which was significantly higher than that of either single agent. In the field experiment, the best control efficacy (67.92%) was achieved when the combined microbial agent was diluted 300-fold. The efficacy of this combined treatment was comparable to that of the chemical pesticide fludioxonil in both pot and field conditions. The combination of the two agents significantly increased the number of OTUs and the alpha diversity indices of both bacterial and fungal communities in the soil. It also significantly increased the relative abundance of beneficial taxa, such as Actinomycetota and Chloroflexota, while reducing the abundance of pathogenic fungi. Furthermore, the combined treatment enhanced the stability and complexity of the microbial network structure in the quinoa rhizosphere. Functional prediction of the microbial communities revealed that the expression of bacterial functions related to amino acid transport and metabolism under the combined treatment was negatively correlated with the incidence of quinoa disease. Within the fungal community, the relative abundance of functional groups such as symbiotrophic and endophytic fungi increased significantly, whereas plant pathogenic groups decreased significantly. Conclusion The combined microbial agent can effectively inhibit the occurrence of quinoa basal stem rot by optimizing the rhizosphere microbial community structure, providing a theoretical basis and a new strategy for the green control of this disease.

Key words: Fusarium solani, Trichoderma afroharzianum, Bacillus velezensis, microbial diversity

ZHANG Wen-jing, MA Xin-rui, XU Zi-lu, LYU Hong, QIN Nan, YIN Hui, ZHAO Xiao-jun, REN Lu. Effects of Combined Application of Trichoderma afroharzianum and Bacillus velezensis on Quinoa Basal Stem Rot and Rhizosphere Microecology[J]. Biotechnology Bulletin, 2026, 42(9): 327-341.

Figures/Tables 12

Table 1 Field control efficacy of different treatments against quinoa basal stem rot

处理 Treatment	发病率 Incidence （%）	防治效果 Control effect （%）
T1	27.92±1.10b	57.86±1.66c
T2	24.17±0.42c	63.52±0.63b
T3	21.25±0.72cd	67.92±1.09ab
T4	30.42±0.83b	54.09±1.26c
T5	19.17±1.82d	71.07±2.74a
T6	66.25±1.44a	-

Fig. 1 Disease occurrence of quinoa basal stem rot under different treatmentsT1: YPTJ-1 WP 500-fold dilution, T2: LMNS-M9 WP 500-fold dilution. T3: Mixed microbial agent WP 500-fold dilution (The ratio of YPTJ-1 WP to LMNS-M9 WP is 7∶3). T4: 50% fludioxonil WP 5 000-fold dilution (positive chemical control). T5: Only F. solani spore suspension (negative control). T6: Only watering water (blank control). The same below

Fig. 2 Pot culture control efficacy of different treatments on quinoa basal stem rotDifferent lowercase letters indicate significant difference (P<0.05), the same below

Fig. 3 Principal coordinate analysis (PCoA) of bacteria (A) and fungi (B) in the quinoa rhizosphere under different treatments

Fig. 4 Relative abundance of bacteria (A) and fungi (B) in the rhizosphere soil of quinoa under different treatments at the phylum levelMicrobial groups with a relative abundance of less than 1% are classified as other, the same below

Fig. 5 Relative abundance of bacteria (A) and fungi (B) in the rhizosphere soil of quinoa under different treatments at the genus level

Fig. 6 Evolutionary branch diagram of differentially abundant microbial species in the quinoa rhizosphere soilThe circles radiated from the inside out in the figures represent the classification levels from genus to phylum. Different color nodes indicate significant enrichment in the corresponding groups, and light yellow nodes indicate microbial groups that have no significant effect on the differences between groups

Fig. 7 LEfSe analysis of bacteria (A) and fungi (B) in quinoa rhizosphere soil

Fig. 8 Co-occurrence network analysis of soil bacteria under different treatmentsCK1: blank control, water only; CK2: negative control, inoculated with F.solani only; D: microbial agent control, B. subtilis treatment; E: compound microbial agent treatment (diluted 300-fold). The same below

Fig. 9 Co-occurrence network analysis of soil fungi under different treatments

Table 2 Topological properties of the co-occurrence network of soil bacterial and fungal communities under different treatments

微生物 Microorganism	处理 Treatment	节点数 Node number	边数 Edge number	平均度 Average degree	平均聚类系数 Average cluster coefficient	平均路径长度 Average path distance	模块化 Modularity
细菌 Bacteria	CK1	100	616	12.32	0.572	3.404	0.558
	CK2	100	1 579	31.58	0.768	2.183	0.384
	D	100	2 464	49.28	0.765	1.843	0.260
	E	100	1 923	38.46	0.764	1.914	0.375
真菌 Fungi	CK1	100	365	7.300	0.516	3.565	1.665
	CK2	97	407	8.392	0.521	3.499	0.710
	D	93	335	7.204	0.572	4.078	1.689
	E	97	430	8.866	0.589	3.790	0.624

Fig. 10 Functional prediction of bacteria (A) and fungi (B, C) in quinoa rhizosphere soil of different treatment groups

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